None of these small-sensor compacts really satisfy at anything over ISO 400, but as these resutls show, squeezing 10 megapixels into such a small space and then including an ISO 800 or higher option is simply asking for trouble. In all our tests we noted that the GX100's noise reduction lurches into overdrive at ISO 800 - not that it helps a great deal; the output still looks noisy, it's just really soft and noisy. This is the equivalent of 'fixing' a rattle in a car by turning the music up a lot louder.